Estimation of Clear-Sky Solar Radiation Using ASHRAE Model for Aligarh , India

Solar radiation is a function of various parameters viz., solar altitude, location (latitude and longitude), site altitude, albedo, atmospheric transmittance and cloudiness. However, clear sky solar radiation is independent of cloudiness index. Analyzing the solar radiation variation on a clear day provides a basis for comparison of cloudiness index for days falling under different sky conditions. Solar radiation (global, diffuse and direct) variation on horizontal surfaces is presently calculated using ASHRAE clear-sky model. The calculated values are validated against the measurements for Aligarh, India (27.88 ̊N, 78.08 ̊E, 192 m.s.l.). Mean bias error, root mean square error and tstatistics methods are used to analyze model performance. The results show that the ASHRAE clear-sky model is suitable to estimate hourly solar radiation in Aligarh, India. Index Terms ASHRAE, clear-sky, estimation, India, statistics.

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